1. Field of the Invention
The present invention relates to the elimination of unreacted methanol from aqueous residual solutions emanating from the synthesis of methyl chloride, and, more especially, to such elimination where the methanol is directly recovered in the form of methyl chloride.
2. Description of the Prior Art
It is known to this art that methyl chloride is produced industrially by reacting methanol with hydrochloric acid, in the liquid or gaseous phase, in the presence of a catalyst. In both cases, the reaction products are obtained in the gaseous form. They essentially consist of methyl chloride, water, hydrochloric acid and unreacted methanol.
The reaction products exiting the reactor are cooled to separate the methyl chloride and to recover an aqueous phase containing the excess hydrochloric acid and the unreacted methanol. The gaseous methyl chloride phase is washed with water, or with an aqueous hydrochloric acid solution having suitable HCl titer, in order to almost completely strip it of the HCl and methanol that may still be retained therein. This wash water may optionally be added to the aqueous phase for subsequent treatment.
In the synthesis of methyl chloride, the aqueous phase which contains more than 15% by weight, and typically in excess of 20% hydrochloric acid, is usually discarded, resulting not only in a loss of methanol in amounts of up to 100 g/l, and most typically from 15 to 60 g/l, but also in pollution, if the effluents are not treated prior to discharge.